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Summer Patch – Turf Disease

Summer Patch is a lawn disease that is active during the summer when turfgrass roots are growing very slowly.  Some of the symptoms you might notice include blade color change from a healthy green to tan-brown, often with a reddish color as they die.  This reddish color is an early symptom of something more severe and often only appears after a small area of grass has died. The dead areas usually appear in rings or circular patches. The fungi in the soil that causes this favors wet soil conditions in the spring and fall and are highly dependent on temperature and moisture conditions. Due to the higher temperatures this year it has been a much more noticeable problem.

Summer Patch

This disease attacks grass root systems and crowns resulting in dark colored, rotted roots and crowns. The spread of the fungi is favored by thick lawns and will easily grow along root systems spreading into the crown. Wet periods followed by dry conditions can bring on severe symptoms. Affected lawns will often die during even slight dry periods since they have no root system to support them. The conditions of the soil in your yard can contribute; compacted soils delay or prevent the establishment of root growth into the existing soil and the turf is weakened as a result of slow water logging and an increase in thatch build up.  Even if you have an inch or two of topsoil it can cause many of the same affects because of soil compaction. Soil prep should include working any topsoil into the existing soil; this helps to create a more uniform, deeper root zone and adds more organic matter as well as helps relieve soil compaction.

Thatch Management

Thatch is a layer of partially decomposed grass; it is on top of the soil and below the blades of grass. It is a natural development of healthy, vigorous turf, but layers greater than ½ inch can cause problems. An excessive layer of thatch will inhibit root growth deeper into the soil which limits access to water as well as other nutrients. The thatch layer can be a location for the fungi to live, overwinter and grow and attack the turf. One of the main practices for reducing thatch is aeration; spring and late summer are good times to reduce thatch. If your lawn is severely thatched it can treated at any time. Aeration removes less thatch directly but speeds up decomposition by bringing soil and thatch directly into contact. Aeration also helps to reduce soil compaction and increase water and nutrient saturation as well as helps to stimulate root development.  If you have heavy clay soil or clay loam soil regular aeration is necessary to prevent your soil from becoming compacted. 


When the weather is hot or in the spring avoid excess use of nitrogen fertilizer.  Oftentimes summer moisture stress is often associated with summer patch development proper watering is critical. What is required is frequent light watering to keep the top ½” to 2” of soil moist. As the lawn begins to recover, gradually lengthen the time between watering and apply more water each time until back to a normal watering program. Watering during the heat of the day is not harmful and even required for cooling the lawn, preventing water stress and associated patch symptom development.


While managing a lawn with Summer Patch Disease mowing heights should be adjusted higher during the recovery period. This will allow the potential for greater rooting depth and consequently more soil volume from which roots can draw moisture and nutrients. This is very important during periods of drought stress; removing about 1” of the grass height at any one time will help minimize plant stress.


Overseeding an existing lawn is usually of limited value.  A greater degree of success can be achieved by either topdressing or thoroughly core aerating the lawn prior to overseeding. This will promote seed-to-soil contact that is essential for germination and seedling development.

Bonide Infuse
Fertilome F-Stop


Preventative fungicide application to sites with a history of disease can be effective when first applied mid-April to Early May and repeat applications (one or two) are made at 3 to 4 week intervals. At Gertens we have a few options that will help you and your lawn overcome Summer Patch; Bonide Infuse (either in liquid or granular form) as well as Fertilome F-Stop granules will help.







Some information from the University of Minnesota Extentsion Services.